Parties were kicking off across the peninsula this morning, but don't believe the hype about Italians celebrating the 150th anniversary of the country's unification. Everybody knows that the real reason behind the festivities was Milan's 1-0 win away at Cagliari. "A Milan who win do good for Italy and strengthen the government," declared Silvio Berlusconi this week. "When we win everybody celebrates with me in parliament and there are happy faces. When we lose they are all a bit more sad."

The smile on Silvio's face will have been that little bit broader after a victory that confirmed Milan as the winter champions. Defeats for Napoli and Juventus and a draw for Lazio allowed the Rossoneri to extend their lead at the top of Serie A to five points, with one round of games remaining until the season's midway stage. The record books show that the winter champions have gone on to win the Scudetto in more than two-thirds of all Serie A seasons.

Not that Milan need to go looking for omens, because far more encouraging than any such statistic was the nature of the victory. The Rossoneri were not at their best – a very long way from it, in fact – but this was a significant result for a side striving to prove they are not Ibra-dependent. Yesterday they were not only without Zlatan Ibrahimovic due to suspension, but also Alessandro Nesta, Andrea Pirlo, Kevin-Prince Boateng, Mathieu Flamini and Gianluca Zambrotta.

In their absence Milan looked flat, uninspired and maybe even a little exhausted from their thinly-disguised marketing expedition to Dubai. With just over 10 minutes to go Cagliari, driven on by a boisterous crowd at the Stadio Sant'Elia, seemed as likely as their hosts to snatch a winner, and had passed up the best chance of the game, Nene failing to convert after the Milan goalkeeper Christian Abbiati passed the ball straight to him inside the area. But then Antonio Cassano came on.

Well, actually what he did first was run around looking for a pair of shinpads. After his own failed to materialise Cassano had to be lent a sweaty pair by the already substituted Gennaro Gattuso. As he stood on the sideline waiting, he looked every bit the man who had shown up in Dubai a week and a half earlier 2.5kg overweight, prompting Ibrahimovic to suggest he needed to go on a "little diet". If Rafael Benítez failed to have his panettone before leaving Milan it may have been because Fantantonio got to it first.

But a lack of fitness is temporary and nobody could really blame him for being a bit out of shape after being kept out of training for two months at Sampdoria. All that will matter to Milan is that he had enough in the tank five minutes after his introduction to sprint on to a neat backheel flick from Robinho and play a delightful disguised pass to Rodney Strasser, who slipped it past Michael Agazzi for the winner.

Strasser may have been a fraction offside but it would have been a marginal decision. Certainly nothing was going to take the shine off the goal for the 20-year-old midfielder, his first for the senior side. "Did you see that pass [Cassano] gave me," he exclaimed breathlessly afterwards. Before the game he had ribbed his team-mate over his Barese dialect. "[Cassano and I] got on immediately, even if I don't understand what he's saying when he speaks. And I speak three languages"

"The next time you say you don't understand when I speak I am going to give you a punch," said Cassano to Strasser as the pair boarded a plane home later that evening but it was meant in good spirits. Strasser, a product of the Milan youth system with three previous Serie A appearances to his name, has already been on the receiving end of a taekwondo kick from Ibrahimovic this season, though the pair are said to be good friends and share a table every day for lunch after training. What he'll make of Cassano's bizarre bottom-grabbing antics, of course, is a whole different matter'

He will continue to have a significant role to play in the coming days. Massimo Ambrosini's yellow card means he is due a suspension, while Gattuso may struggle to recover in time for the game against Udinese on Sunday following a knock to the thigh. So too will his fellow youth team graduate Alexander Merkel, who started yesterday's game. A committed effort to bring through such players this season would represent perhaps an even greater step forwards for Milan than that which has already been achieved in the league standings.

Almost the perfect weekend for Milan, then, but yesterday evening brought a note of caution from their own stadium, hand-delivered by one of their own former stars. Leonardo was almost as impressive in his debut on the Internazionale bench as Cassano had been coming off it for their rivals, his team swatting aside a Napoli side who had come into the game joint-second and boasting the second-best away record in the league. More impressively still, they did it without Júlio César, Wesley Sneijder, Samuel Eto'o or Walter Samuel.

"I don't want to understand, I want to live," declared Leonardo after admitting he was "surprised" by the ease of his team's victory. It is hard to imagine such a statement ever falling from the lips of the self-consciously studious Benítez, though he too was acclaimed by the home support. "Benítez: A sincere thanks from us, the only ones who always backed you," read a large banner hung from the upper tier. "And now full faith in Leo"

Leonardo was quick to play down his own impact and will know there is a very long road ahead. His team kicked off 16 points behind Milan, and though they can close the gap to seven if they win their games in hand, it is also true that no Inter coach has won both their first two games in charge since Luigi Simoni in 1997 (and Leonardo is Inter's 12th manager since then). A visit to Catania, beaten just once at home so far this season, on Sunday will be no walk in the park.

But as long as he can keep his team playing with the enterprise they showed yesterday, Inter will have hope. If Thiago Motta can stay healthy long enough to contribute a few more goals like this, we may see a few a few frowns in parliament yet.

Talking points

• If it was a happy return to action or the Milan clubs it was anything but for Juventus. To lose 4-1 at home to Parma was humiliating, for Sebastian Giovinco, who they loaned to Parma, to get two of the goals – even if he didn't celebrate – was infuriating, but to lose Fabio Quagliarella for the rest of the season to a cruciate ligament injury was just plain crushing. The Bianconeri were already in advanced negotiations to sign Luca Toni from Genoa but with Vincenzo Iaquinta already ruled out for three weeks they will surely need to come up with something more than an ageing forward who has scored just three times in 15 games. Their top scorer will not be easily replaced.

• One-nil up, 2-1 down, then 4-2 winners. Life is never dull for Roma, is it? There was much uproar in this morning's papers over two of their goals – John Arne Riise seemed to carry the ball over the line before cutting it back for Marco Borriello to equalise at 2-2, and then Mirko Vucinic was in an offside position when he was played in to put Roma back ahead. Having said all that, Borriello's goal might well have been prevented if the defenders had played to the whistle and tried to stop him from scoring, instead of standing around with their hands in the air appealing while he nudged it into an unguarded net.

• Another Roma forward, Stefano Okaka, scored the only goal of Serie A's first Puglia derby in a decade. Okaka, who joined Bari on loan, may have been marginally offside too, not that the away fans in the Curva Sud was complaining as he charged towards them after the goal, tumbling over advertising hoardings as he went. This was a huge win for last-placed Bari, their first away from home all season, but also for all those who successfully campaigned against an initial decision by local authorities to play the game behind closed doors. The game may not have sold out, as many had claimed it would, but beyond the ubiquitous paper bombs, the fans were mostly well behaved.

• Adrian Mutu is expected to explain his bizarre departure from a Fiorentina training session at a press conference this afternoon, but even as the club contemplated legal action against him, things continued to fall apart elsewhere. Their draw at Bologna was marred by Marco Marchionni's furious reaction to being substituted after an hour, while the club is struggling to convince a number of players including Riccardo Montolivo to put pen to paper on new contracts. For all the talent in the squad, Fiorentina are only two places outside the relegation zone.

• Is it just me, or of the (few) goals in Serie A this season, have an abnormally high number been rather brilliant? Another classy strike from Antonio Di Natale.